Abstract

This study investigated the potential of biogas production from three (3) constructed wetland macrophytes: Water hyacinth (WH), cattail (CT) and Cyperus papyrus (CP). The digesters used had capacity of 0.22 cm³ each. They were operated under anaerobic conditions with organic loading rate (ORL) of 0.2 kg VS/m³.day and hydraulic retention time (HRT) of 5 days. Observations were made for a period of 128 days. The results show that the three macrophytes produced methane (CH₄) and carbon dioxide (CO₂) in reasonable quantities. The other gases such as H₂S and CO were present in minute quantities only. The results show mean biogas production flows of 38.52±13.05, 75.63±14.34 and 38.52±13.05 mL/kg VS for WH, CT and CP respectively. The mean percentage CH₄ production for WH, CT and CP were 54.45±6.86, 42.02±11.10 and 38.52±13.05%, respectively. The corresponding mean percentage CO₂ productions were 42.71±3.0, 39.73±4.48 and 43.24±2.96%. The energy potentials in terms of calorific value were 9.22, 7.02 and 6.13 W/kg of biomass for WH, CT and CP respectively. It was concluded that from water hyacinth alone, a conservative off-grid renewable energy of about 11,825 MW/year is possible as addition to reduce the Nigerian energy demand gap.

Key words: Renewable energy, biogas, macrophytes, constructed wetland, Nigeria.